I assume that you are using MAS Epoxy and the pumps that come with a CLC kit.  If so, it is the viscosity when working at that temp.  If you warm the epoxy by sitting it in a sink of warm water for a few minutes, the pump will work much better.  Warming the epoxy will cause it to kick off a little faster.  When wetting out fiberglass, you will want both the epoxy and your workspace warm.  Work with small batches. 

   i ditched my pumps a boat or two ago. I use disposable plastic drinking cups. Using a syringe for measuring quantities and marking the level on the side. I have a few ready to go whenever I start.

   I agree with Craig on the pump issue. I also gave up on them quite a few years ago, being a waste of resin/hardner and an enless source of hassle. If your doing a big project and mixing on a daily basis I can justify their use, otherwise it's best to mix in a graduated pot. I found a great one at US Composites. Their 8 oz. cups are polypropelene graduated in oz/ml and marked in red. If you happen to leave any residue at the bottom to harden, particularily with a wooden stirring stick, it shoud pop out the next day as an epoxy 'lollipop'. At $6.00 for a sleeve of 25 they may last some folks for years. Their resin prices are also quite reasonable...

I just checked out US Composites web site. I wish I had seen this before I started my Dory build! Several applicators that would have been really nice, they sell empty calking tubes!! That would have been great for laying down the fillets. Oh well, after I win the lottery and start my next boat build I will be ready!!   

I live in So Cal at the usual temps here are 75-90 and I have problems the that pump too. I use blue solo cups to measure now.